Barrett's Esophagus (BE) is the only known precursor lesion for esophageal adenocarcinoma, which is the fastest rising cancer in Caucasian men in the United States. The age of onset of BE is unknown. BE results from chronic gastroesophageal reflux disease (GERD), which is known to develop during childhood. Hence, childhood GERD could be a risk factor for BE. The goal of the proposed research is to examine the epidemiology of BE in children and adolescents using retrospective as well as prospective data collected in the multicenter network project known as Pediatric Endoscopy Database System-Clinical Outcomes Research Initiative (PEDS-CORI). The Specific Aims are (1) to determine the prevalence of BE as defined by endoscopic and histologic criteria in children and adolescents undergoing upper endoscopy; and (2) to evaluate the demographic features (age, gender, ethnicity) and clinical determinants (comorbidity, GERD symptoms) of BE as defined by uniform endoscopic and histologic criteria among children and adolescents undergoing endoscopy. These aims will be achieved through two cross-sectional studies designed to obtain estimates of the prevalence of BE: a retrospective study using information collected from all PEDS-CORI sites between 1999 and 2004 (an expected 16,000 procedures), followed by a one-year prospective endoscopic study in three PEDS-CORI sites (an expected 1,800 procedures), in which additional BE-specific information will be collected. The prospective study includes rigorous standardization of the observation and recording of endoscopic and histologic findings and specific questions about potential risk factors. The long-term objectives of this research are to lay the groundwork in terms of feasibility and sample size for a prospective multicenter study involving all PEDS-CORI sites that will examine the risk factors for BE in children and adolescents.